The present invention relates to a needle of the biopsy type or for taking other samples from human or animal organs. In general, such needles comprise an external cannula and a stem that can slide within the cannula and can be controlled independently of the latter. The cannula has one end fixed to a manipulating element, whilst the other end is tapered or beveled, with a sharp edged mouth designed to penetrate into tissue. The stem with its end that is distal with respect to the grip is designed to close: the mouth of the cannula from inside. The stem moreover has a recessed area developed for a certain stretch in the vicinity of the aforesaid end in order to contain a specimen of tissue taken from the organ concerned by means of a well-known manipulation technique.
The aforesaid needles present the drawback that the amount of tissue, sampled is small in so far as the aforementioned recessed area occupies only one part of the section of the stem, in general one half. Consequently, in order to take a sufficient amount of tissue, it is necessary to use a needle of considerable thickness. In addition, the tissue, which in general has a gelatinous consistency may easily get lost or contaminated during manipulation of the elements of the needle.
The document SU 1537232 describes a biopsy needle comprising an external cannula having a rectangular cross section, and a flexible closing element, which can slide inside the cannula. At a point corresponding to the tip of the cannula, the latter has lateral guide grooves in which said closing element engages, so as to be deflected and thus close the opening of the needle both to enable the first step of penetration of the needle into the body of the patient without collecting any material and to enclose a specimen of tissue before extraction of the needle. The above conformation does not, however, afford the possibility of extracting the tissue specimen from the needle while still leaving the external cannula of the needle itself in situ in the body of the patient, for checking the quality of the tissue sampled and possibly repeating the sampling operation at a greater depth.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.
One purpose of the present invention is to overcome the above-mentioned drawbacks; other advantages will emerge from the ensuing description and claims.
A biopsy needle according to the invention comprises a cannula with a sharpened front end that is tapered or beveled, and a stem designed to close the mouth of the cannula in a known way. The cannula has, for a certain stretch in the vicinity of the mouth, a first portion of relatively small thickness and a second portion in an area corresponding to the mouth of a larger thickness, the two portions forming between them, inside the cannula, a step-like, portion developed according to an inclined plane with respect to the axis of the cannula. Between the cannula and the stem there is inserted an axially slidable element for withholding the tissue specimen, said slidable element being controllable independently of the stem and of the cannula. Said element has, in the vicinity of said internal step-like portion of the cannula, an end provided with a tab-like extension which, by means of the relative sliding between the slidable element and the cannula and in the direction of the mouth of the latter, is designed to engage at the front with the step-like portion in order to bend, so closing the, mouth of the cannula, thus cutting the tissue specimen that is being sampled and withholding it inside the withholding element during extraction of the latter and ,possibly also of the needle. In this way, the specimen has a right cross section equal to that of the mouth of the cannula and is withheld securely inside the latter both during extraction of the needle from the organ concerned and afterwards. The tab like extension preferably has a restricted area of connection with the withholding element in order to facilitate bending thereof, the said bending occurring beyond the elastic limit of the tab itself and thus generally being permanent.
In a particular embodiment of the invention, the tab-like extension (tab extension) has side walls that are designed to contain the tissue specimen laterally.
The external cannula may have a polygonal cross section, for example a square cross section, or even a circular or elliptical cross section.
The arrangement according to the invention can be applied, both to needles for taking samples of soft tissue and to needles for taking intraosseous samples.
In particular embodiments of the invention, there may be provided, between the withholding element and the stem for closing the needle, a further axially slidable element, generally of a tubular shape. This additional element is configured so that it can be set in contrast with said tab extension of the withholding element, once the tab extension is bent, then to re-open the tab extension in the specimen-extraction step, so as to facilitate extraction of the tissue specimen without damaging it, as will be described in greater detail in what follows.